1. Field of the Invention
The invention relates to a pneumatic conveyor for transporting bulk materials, particularly tablets, having a compressor for conveyor gas, a bulk material feed unit and a bulk material discharge unit, and a conveying line that connects the latter, wherein a return line for the conveyor gas is provided between the bulk material discharge unit and the compressor, so that the conveyor gas is conducted in a conveyor gas circuit.
Furthermore, the invention relates to a method for operation of a pneumatic conveyor, particularly for conveying tablets.
2. Description of the Related Art
Such a conveyor and a method for its operation, for transferring granulated or powder-form material such as sugar from a truck to a storage container of a bakery, are known from U.S. Pat. No. 2,814,531.
The sugar is transported pneumatically from the transport container into the customer's storage container. Such transport procedures can take hours until they are completed. During the transfer time, it is necessary that the operational sequences in the factory continue to take place without disruption. In this connection, it must, of course, also be possible to draw partial amounts of the sugar from the storage container, while new sugar is being transferred into the storage container.
Depending on the pressure conditions, which are a function of the operating state, it can happen, when drawing off transferred sugar, that the sugar is blown into the environment. In order to prevent this, a container having a filter is proposed, among other things, which container has pressure equalization valves on both sides of the filter, so that the pressure can be set as desired, and no sugar gets into the environment. In this container, which is disposed in the feedback line, dust also collects in front of the filter in the flow direction, which dust can then be removed from the container as needed. The interface between the storage container and the supply container is placed in such a manner that the filtered material, together with the blower and the transport tank, remains on a truck after the conveying line and the return line have been disconnected.
In the system described in U.S. Pat. No. 2,814,531, it is necessary to remove the filtered dust from the separation chamber provided, i.e. the container having the pressure equalization valves. Furthermore, it can happen that dust enters into the environment if the filter is defective.
As long as foods are involved, as provided in this prior art, such disruptions in operation can be tolerated. However, this situation can be assessed differently when conveying materials that can contaminate the environment. This requires particular attention in the production of tablets, because their ingredients can be harmful for the operating personnel if specific dosages are exceeded.